Energy Efficient Windows With A Vacuum?

The Low E coating would be required regardless of the technology of insulation.

We rarely even see double pane glass in Florida. At first I thought that was strange, but when you think about it, we really don't have a large delta of temperature extremes here. Yes, we may get down to 0°C on occasion, but that is rare.

In the summer the temperature difference between inside and outside is rarely more than 10°C. Humidity and direct sunlight are the bigger issues, so Low E glass is a must.

I'm curious, how well does a single pane window withstand hurricane force winds? I would think most insurance companies would say not very well.

A) That's why you typically 'board up' windows with Plywood when a hurricane is expected.

B) Blowing out the windows may be a 'structural fuse,' so that the building changes from a 'closed structure' to an 'open structure' and does not experience such a strong pressure differential that would crush or shatter it.

Right. I was thinking of new construction.

Don't people put boards up over windows when a hurricane is forecast in the USA? I am sure I have seen newsreel film showing that, but don't ask me when or even "if"!!

I know I would.....

Yes they do board up windows when dangerously strong winds are expected. It's to protect the glass from impacts. The boarding up procedure typically leaves 'vents' or 'gaps' so that the house interior can change its air pressure to match the outside. You don't want the house so sealed up the structure gets crushed or blown apart by pressure differentials.

Most windows will stand up to hurricane force winds no problem....I lived here starting in the 50's and have been hit with several hurricanes, never had a window break....it's mostly the flying debris that can break a window, that's why coverage is needed....most people have awnings now...we used to just tape them up...I can still remember back around 1960 hurricane Donna hit us dead on, went out during the eye, it was wild...but I can remember watching the sliding glass doors we had on the back bowing in and out violently oscillating I was sure they were going to break, but no they held out...

Interesting, that must also have been good quality glass as well.....

A common failing with early vacuum sealed double glazed window units was the seal hardening and cracking destroying the vacuum. At least you could see where they had failed, a fan shape of moisture would form at the point of failure.
There was nothing you could do about it other than replace the unit. If you didn't you could watch the green goo as it spread between the glass.

That was 30+ years back, they have improved since. I hope they have, all my windows are sealed units.

Correction:

They don't use vacuum now. Silica gel and argon injection seems to be the way.

https://www.youtube.com/watch?v=qbxSgtUIpj4

Apparently, that is not a barrier to making such windows.

This company did in 2013 and another Japanese company has already been doing it.

However, the product doesn't seem to have taken off. Other companies have done it, but the total cost is high and the return on invest from energy savings is small.

Using glass spacers, in my book, is structurally like using many small windows. It does seem to offer one solution to the thickness issue.

Cost still seems to be a problem as the product mentioned in the article is not yet to market.

I doubt that even if you hit cost parity, and it won't, 5% savings on energy is not going to send the world beating a path to your door.

There is mention of spacers, and keeping them invisible or at least inconspicuous. Thin flat pieces cannot resist much pressure differential without deflection, so more is going on with this than just two sheets with a partial vacuum between.

GA.

It would have to be thick enough to survive a rifle bullet!! Or the panes would be pressed together!!!

Holding a vacuum is indeed a challenge, but there is research underway that shows some promise...

https://en.wikipedia.org/wiki/Materials_for_use_in_vacuum

https://en.wikipedia.org/wiki/Insulated_glazing

http://www.aamanet.org/news/2/10/0/all/1086/coming-soon-to-a-window-near-you-vacuum-insulated-glazing

I had seen such windows way back in 1978 when I visited Germany- but vacuum had leaked etc. I have seen US patents of double walled glass panes with glass structs to support glass (like pillars in a large building with huge ceiling). The practical difficulty is differential temperature in glass as you try to weld over longer lengths leads to stresses / strains and cracking immediately or after a few minutes / hours. Welding / stitching with glass is not as easy as with metal. If somebody can do it- I too am interested for another project.

So simplest solution is to fix two separate glass sheets with air gap- with air pocket- cannot be vacuum (practical fabrication difficulty).

Older gas filled windows have leaked here in Germany.....let alone vacuum ones.....

If you think about it, when the weld containing the vacuum between the two sheets of glass fails (and it will), the vacuum will start to draw debris into the space between the panes.

This debris can consist of dust or moisture, or both. resulting in a "dirty" appearance.

The gas filled window will also fail at some point but material will less likely be drawn into the interstitial space between panes.

Double-walled tanks that utilized the annular space for insulating purposes generally have a an evacuation port for connection to a vacuum pump or some indicator that the vacuum has failed.

Have you ever had to replace your thermos because it failed to keep its content at the proper temperature?

The only fail of keeping temperature is when I knock the thermos off my desk and it shatters. It's all one piece of blown glass. I should post a picture of it.

Vacuum flasks are usually cylindrical with domed ends. The vacuum port is always placed in the outer shell (for manufacturing reasons) and in an area that is curved in two directions (for structural reasons). Exerting a force onto the face of flat glass makes it deflect. The curvature transfers the vacuum force on the inner shell into tension and on the outer shell into compression. Glass is better able to withstand a tension or compression force than a deflection force. A sphere is the only shape that would better withstand the imposed pressures.

Vacuum windows are used in the camera industry to insulate CCD sensors at extreme low temperatures, We use them for cameras cooled to -40°C but these are small, maybe around 40mm diameter, & the gap is large, perhaps 50mm. As stated in other posts, doing this over a large area is problematic.

Large areas may be problematic however aren't TV tubes a vacuum?

Its the shape and sheer weight of glass that keeps a tube OK, plus its not a true vacuum, it has some inert gas in there....

Thanks to you and dery2026 for your knowledgeable contributions.

I can't see much practical advantage to vacuum sealed glass windows, except in extreme climates, maybe. Here in Arizona we just put shades or awnings outside the west facing windows.

I have them at my condo. At 13 years old, the vacuum seal has failed allowing for regular humid air to get in. This results in windows that "fogs" inside, between the two panes of glass or frosts in the same way. The windows were made to look like a traditional six pane window with the separation "frames" actually in between the two panes of glass. AS for insulation, the three that are still intact do feel warmer to the touch than those that have obviously failed, and at sub zero temps the failed windows do frost on the inside unlike those that have not failed.

If I am understanding the people here, most windows have a dry gas between the panes.

Its seldom that they have a true vacuum, and as you can read here, the supporting disks when they are, are obvious from several feet away.....also such windows are quite small....

I personally have not seen double glazing with a vacuum between the panes....ever....

I hope this helps.

Glassman made a good post today, you should read it.....

Andy, what a brilliant discourse.

And your willingness to further impart knowledge on those less learned than yourself is a generous act as well. "if you or anyone else has any further questions, I will do my best to answer them for you."

I am constantly amazed by your vast knowledge.

Except, of course, on those times when it is only half vast.

....and as expected, you "outed" yourself for the umpteenth time.....

Even faster than I thought you would!!!and you still don't know why you react to my prodding!!!

If I were as good a fisherman, as I understand certain types of people and how they tick, I would be the richest fisherman around!!!

I am wondering whether there is more heat loss from the use of aluminum (versus Wood) in modern window construction.

Thermal transfer through the spacer is the target. Window frame material isn't quite as significant, especially with the air pocket designs of today's frame and sash sections.

The windows we generally install in Germany have a steel frame, but the glass is not allowed to make contact, it is thermally insulated from the inner and the outer steel frames.

Also, the "outer" steel, is not in contact with the "inner" steel, to prevent forming a cold/hot "bridge.

The steel is coated with a thick plastic coat to prevent rust and to make the windows more attractive, no painting required.

It is not the vacuum that makes the thermos so very efficient. It is the mirrored surfaces that reflect the heat that gives it it's extra punch. If you mirrored your windows so they didn't let heat and light in,... there would be no need for the windows.

So, if you have a mirrored ceilings, it obviates the need for insulation in the attic?

Funny, seems like this would have been noticed somewhere back in the 60's or 70's.

Who could have afforded that?

Cocaine is know for not being very affordable either, yet large quantities of that were consumed in the 60's and 70's. .... in fact I'd bet chances are much higher cocaine has been done in a room if it has a mirrored ceiling.

Voice of experience?

'Good decisions come from experience. Experience comes from making bad decisions' - Mark Twain

.

Though, I've never had mirrored ceilings, so perhaps my decisions aren't that good.

Many amateur Porn film directors maybe?

The silvering of the thermos might reduce the heat transfer to some extent, but it's the vacuum that provides the bulk of the insulation.

I had 15 years experience testing cryogenic receivers, and the better the vacuum, the lower the pressure increase due to boil-off.

LOL!!

How true.....a bit of insulated wall would be far more effective!! Maybe with a TV camera and inside a large flat screen TV?

20 of those and the need for windows is severely reduced!!

Has anyone used transparent material other than glass for windows- like polyester or polypropylene sheets? Are these banned due to fire safety issues?

Has man developed any material- other than glass - which is transparent and can hold vacuum of the order of say 1 mm of mercury for a decade or longer? Can it be molded?

There was a 50,000 sq ft entertainment venue called Summerland, located at Douglas in the Isle of Man and designed to cater for 10,000 tourist visitors. There were dance floors, restaurants, games rooms, and public bars. The roof and front wall of the complex was covered in Oroglas™ a transparent acrylic sheeting. A fire in August 1973 a couple of years after it opened killed fifty people and injured a further eighty. The sheeting was not the only factor to the high number of deaths but was a significant contributor. Fire codes were amended after the fire to ban the use of similar materials for buildings in the UK. The island's tourist industry never recovered and it now relies on its status as an offshore tax haven and financial services center for it's main revenue.

Yes, energy efficient windows are cost prohibitive this is also good but nowadays impact windows are new in the market for installation also pgt windows, siw windows, vinyl windows are also available .Take the help of an expert while installing the window like siw windows or pgt windows like this for better look to your house and also provide services for installation. If your house is in hurricane prone areas, then installed impact windows and doors or hurricane protection doors and windows.